Most high explosive fragmentation projectiles are anisotropic in their fragmentation pattern. In terms of a coordinate system where the forward direction of the projectile is designated 0.degree. and the rear direction 180.degree., zones of constant angle will usually have a constant average fragmentation density when averaged over many detonations of the same type of shell. The zone of maximum fragmentation density will usually occur at or near 90.degree. for stationary or slow moving projectiles. For a fast moving projectile the forward velocity of the projectile will add vectorially to the predominantly sideward velocity of the explosive force resulting in the zone of densest fragmentation being swept forward to form an annular cone with a half angle of typically 30.degree. to 60.degree. for various types of shells. This zone will typically have a fragmentation density 5 to 12 times greater than the average fragmentation density. This is so whether the density is measured in weight of fragments per steradian or number of fragments per steradian. This zone (Z max) typically about 10.degree. wide may contain about half of the total fragmentation yield of the projectile. An optimum fuzing method is one in which detonation is made to occur so that Z max will consistently impact the desired target. Existing types of optimum fuzing have attempted to define the optimum plane above the target at which detonation of a salvo of fragmentation projectiles will place the densest part of the fragmentation pattern at the target. An example of an existing optimum fuze is an anti-aircraft fuze which uses a infrared detector with an annular field of view matched to the Z max angle for the expected encounter scenario. This fuze will detect the hot exhaust of the jet engine and detonate the shell at the optimum time. This is a passive optimum I.R. fuze. Another example of an optimum fuze is a microwave fuze which is used to dentoate a shell when its target is at an optimum angle. This is an active optimum microwave fuze. Both these types of optimum fuzes depend on a detector in the projectile identifying the target as well as indicating the optimum angle. Their use however, is limited to targets which are uniquely different from the environment in some easily characterizable way such as, for example, targets having strong I.R. sources or having high R.F. reflectivity. Although most targets do not display such characteristics, the prior art fuzes found wide use and, when used, some have displayed reliable accuracy.